Portable nanoparticle sampler

ABSTRACT

A portable nanoparticle sampler for collecting respirable particulate matters and nanoparticles is composed of a tangential flow cyclone, a multi-microorifice impactor and a filter cassette. The tangential flow cyclone can remove the microparticles with cutoff aerodynamic diameter (dpa) larger than 4 μm and guide the airflow to the multi-microorifice impactor located below the cyclone. The multi-microorifice impactor includes a multi-orifice nozzle and a rotary impaction plate for enabling the microparticles with dpa from 100 nm to 4 μm to be uniformly collected on a silicon-oil-coated impaction substrate. The remanent microparticles with dpa smaller than 100 nm are collected by the filter cassette. Therefore, compared with the prior art, the portable nanoparticle sampler is characterized by low pressure loss and accurate microparticle sizing to meet the requirement of nanoparticle sampling at workplaces.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a microparticle sampler andmore particularly, to a portable nanoparticle (NP) sampler.

2. Description of the Related Art

According to many studies, inhaled NPs pose a high adverse effect onhuman health. To assess the occupational health risk due to the exposureto the NPs in workplaces, it is necessary to collect the NPs of variousdiameters for further analysis of their ingredients.

A variety of NP samplers have been commercially available, includingelectric low-pressure impactor (ELPI), low-pressure impactor (LPI),microorifice uniform deposition impactor (MOUDI), and nano micro-orificeuniform deposition impactor (Nano-MOUDI). However, such samplers are toolarge and too heavy. Besides, the flow rate and the pressure loss aretoo high in the process of sampling to make the samplers work with smallportable pumps. Thus, they could only be put at a fixed location forcollecting NPs.

To measure the particle concentration at the actual workplaces moreaccurately, the inventors of the present invention successfullydeveloped a personal NP sampler as disclosed in U.S. Pat. Laid-open No.2009/0272202. The personal NP sampler is composed of a per-classifier, anozzle, a particle-sizing filter pack, and a final filter pack frombottom to top for guiding an airflow from bottom to top to enable theairflow to be filtered by a particle-sizing filter and the final filter.Although such personal NP sampler can collect the NPs of differentdiameters via two stages and be applied to the small pump, the cutoffdiameter of the particle-sizing filter is related to the flow rate ofthe airflow thereat and the flow rate is subject to the invariablenumber of the pores of the particle-sizing filter in such a way that adeviation happens between the cutoff diameter thereat and the default.

In other words, the aforesaid personal NP sampler though has hadpreferable portability but the cutoff diameter is subject to slightinaccuracy, so it still needs further improvement.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide an NPsampler, which is portable and precise at the same time.

The foregoing objective of the present invention is attained by the NPsampler composed of a tangential flow cyclone, a multi-microorificeimpactor located below the tangential flow cyclone, and a filtercassette located below the multi-microorifice impactor.

The tangential flow cyclone includes a cyclone body and an outflow duct.The cyclone body is formed of an annular portion, a top plate, and abottom plate. The top plate and the bottom plate are mounted to a topside and a bottom side of the annular portion, respectively. A firstchamber is defined between the annular portion, the top plate, and thebottom plate. An inlet is formed on the annular portion forcommunication with the first chamber. The outflow duct runs through thebottom plate and is provided with an entrance and an exit. The entranceis located inside the first chamber and higher than the inlet inelevation. The outflow duct allows a gas entering the first chamber todownwardly pass through the entrance and the exit and then to exit thetangential flow cyclone.

The multi-microorifice impactor includes an impaction body, a nozzlebase, and an impaction plate. The impaction body defines a secondchamber. The nozzle base has multiple microorifice nozzles communicatingwith the exit and the second chamber. The impaction plate is locatedinside the second chamber and right beneath the nozzle base.

The filter cassette defines a third chamber and includes a guidepassage, an outlet, and a filter. The filter is mounted inside the thirdchamber and partitions the third chamber into a filtration chamber andan outtake chamber. The guide passage communicates with the secondchamber and the filtration chamber. The outlet communicates with theouttake chamber.

The output airflow exiting the tangential flow cyclone through the exitis downward and the multi-microorifice impactor is employed, so the NPsampler of the present invention has lower pressure loss for workingwith a small pump. Besides, the cutoff diameter of the respirableparticulate mass (RPM) collected by the multi-microorifice impactor atthe second stage can be precisely maintained to the default without anydeviation to help further analysis and comparison to reach the aforesaidobjective of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a preferred embodiment of the presentinvention.

FIG. 2 is a sectional view of the preferred embodiment of the presentinvention.

FIG. 3 is a top view of a nozzle base of the preferred embodiment of thepresent invention.

FIG. 4 is an enlarged view of a part of the preferred embodiment of thepresent invention, illustrating the nozzle base and the impaction plate.

FIG. 5 is a schematic view of the preferred embodiment of the presentinvention at work.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1-2, a portable NP sampler constructed according to apreferred embodiment of the present invention is composed of atangential flow cyclone 10, a multi-microorifice impactor 20 locatedbelow the tangential flow cyclone 10, and a filter cassette 30 locatedbelow the multi-microorifice impactor 20. The detailed descriptions andoperations of these elements as well as their interrelation are recitedin the respective paragraphs as follows. Note that the phrases “top”,“bottom”, “high”, “lower”, and “upper” are defined while the portable NPsampler is erect on the ground, i.e. according to the relative positionsin gravity.

The tangential flow cyclone 10 includes a cyclone body 11 and an outflowduct 12. The cyclone body 11 has an annular portion 111, a top plate 112mounted to a top side of the annular portion 111, and a bottom plate 113mounted to a bottom side of the annular portion 111. A first chamber 114is defined between the annular portion 111, the top plate 112, and thebottom plate 113. An inlet 115 is formed on the annular portion 111 forcommunication with the first chamber 114 and axially parallel to animaginary tangential direction of an internal surface of the annularportion 111. The outflow duct 12 runs through the bottom plate 113 andhas an entrance 121 and an exit 122. The inlet 121 is located inside thefirst chamber 114 and higher than the inlet 115 in elevation, so theoutflow duct 12 can allow the airflow entering the first chamber 114 todownwardly exit the tangential flow cyclone 10 through the entrance 121and the exit 122. In this embodiment, the inlet 115 has a squarecross-section; on the premise that the flow rate keeps constant at 2L/min, the diameter of the inlet 115 is 2.1 mm×2.1 mm, the cutoffdiameter of the tangential flow cyclone is 4 μm.

To facilitate cleaning the first chamber 114, the bottom plate 113 canbe designed to be detachably mounted to a bottom end of the annularportion 111 by threaded connection or alternative proper means. Theoutflow duct 12 is combined to the bottom plate 113, so when the bottomplate 113 and the annular portion 111 are separated from each other, theoutflow duct 12 can be detached apart from the annular portion 111.

The multi-microorifice impactor 20 includes an impaction body 21, anozzle base 22, and an impaction plate 23. The impaction body 21 definesa second chamber 24 therein and is formed of an upper half part 211 anda lower half part 212. The nozzle base 22 is arranged between theimpaction body 21 and the outflow duct 12. As shown in FIG. 3, thenozzle base 22 includes multiple nozzles 221 communicating with the exit122 and the second chamber 24, respectively. The impaction plate 23 islocated inside the second chamber 24 and right beneath the nozzle base22. A predetermined gap is formed between a peripheral edge of theimpaction plate 23 and a peripheral wall of the second chamber 24.

To reduce the circumstances that the nozzles 221 are jammed bymicroparticles, each of the nozzles 221 is provided with a smoothannular wall, a longitudinal cross-section of which is arc-shaped, andhas an upper opening 223 and a lower opening 224, as shown in FIG. 4.The lower opening 224 is smaller than the upper opening 223 in diameter.To avoid or reduce particle bounce, the multi-microorifice impactor 20further includes an impaction substrate 25 disposed on a top side of theimpaction plate 23 and coated with silicon oil 251. To prevent thesilicon oil 251 from dispersion resulting from air jet and to furtheravoid particle bounce, the impaction substrate 25 can preferably be aTeflon filter with a pore size of 10 μm, having a plurality of pores 252for preventing dispersion of the silicon oil and effectively avoidingparticle bounce. Alternatively, the impaction substrate 25 can beexcluded from the present invention. Besides, to facilitate weighingafter sampling, an aluminum foil 26 or a thin support piece made ofother material can be mounted between the impaction substrate 25 and theimpaction plate 23. In this way, the aluminum foil 26, the impactionsubstrate 25, and the silicon oil 251 can be weighed as well ascollected microparticles after the sampling.

Let reference character W denote the diameter of the lower opening 224of each nozzle 221. Let reference character S denote the distancebetween the lower opening 224 and the top side of the impaction plate 23because the surface of the impaction substrate 25 is regarded as theextension of the top side of the impaction plate 23 and the silicon oil251 is subject to dispersion resulting from the air jet to be appressedonto the surface of the impaction substrate 25. The number of thenozzles 221 is 137 as an example. When the specific value (S/W) is 13.8,the cutoff diameter of the multi-microorifice impactor 20 is about 100nm, i.e. the microparticles with diameters of 100 nm to 4 μm will becollected by the multi-microorifice impactor 20. The cutoff diameter ofthe multi-microorifice impactor 20 can be precisely controlled by changeof the aforesaid specific value. In practice, the cutoff diameter of themulti-microorifice impactor 20 is not limited to 100 nm.

In addition, to make the distribution of the microparticles be moreuniform, the multi-microorifice impactor 20 can further include afastening plate 27 and a motor 28, both of which are located inside thesecond chamber 24. The fastening plate 27 partitions the second chamber24 into an upper chamber 241 and a lower chamber 242. The fasteningplate 27 includes an axial hole 271 and a U-shaped flow guide hole 272communicating with the upper and lower chambers 241 and 242. The motor28 includes a rotary shaft 281 inserted into the axial hole 271 andsynchronically rotatably connected to the impaction plate 23. Theimpaction plate 23 and the motor 28 are located inside the upper andlower chambers 241 and 242, respectively. When the rotary shaft 281 ofthe motor 28 is rotated, the impaction plate 23 can be driven forrotation together at a predetermined 1 rpm in such a way that themicroparticles can be distributed preferably uniformly on the impactionsubstrate 25 to effectively avoid particle bounce occurring when themicroparticles are centered to particular positions.

The filter cassette 30 defines a third chamber 31 therein and includes aguide passage 32, an outlet 33, and a filter 34. The filter 34 ismounted to the third chamber 31 to partition the third chamber 31 into afiltration chamber 311 and an outtake chamber 312 for collecting theremanent microparticles indicating those with a size smaller than 10 nmin this embodiment. The guide passage 32 communicates with the lowerchamber 242 and the filtration chamber 311. The outlet 33 communicateswith the outtake chamber 312 and is connected with a pipingcommunicating with a suction pump, which is portable, such as portablehigh-pressure-loss pump (Model No. XR5000) developed by SKC Inc., PA,USA, 8 cm (Length)×6 cm (Width)×10 cm (Height), 1054 g (Weight; batteryincluded); its size and weight facilitate a user to carry it withhimself or herself. Besides, to increase the flow rate of the airflowfrom the second chamber 24 to the third chamber 31, the second chamber24 can have a taper-shaped bottom side. However, the bottom side of thesecond chamber 24 is not limited to taper in shape.

Furthermore, the NP sampler of the present invention can further includea plurality of fastening bars 40 for forcing the tangential flow cyclone10 and the filter cassette 30 to approach toward the multi-microorificeimpactor 20 for fixation.

Referring to FIG. 5, in operation, when a suction pump is used forpumping the air, the airflow enters the first chamber 114 through theinlet 115 of the tangential flow cyclone 10 and firstly flows spirallydownwardly along the internal wall of the annular portion 111 subject tothe gravity and inertial action to enable the microparticles of largerdiameters to be thrown to the internal wall of the annular portion 111and then sunk on the bottom plate 113. When flowing to the bottom plate113, the airflow can flow spirally upwardly along an external wall ofthe outflow duct 12 and finally exit the tangential flow cyclone 10through the entrance 121 and exit 122 by order. In this embodiment, thecutoff diameter of the tangential flow cyclone 10 is about 4 μm.

The airflow continues to pass through the nozzles 221, flow along thegap between the impaction plate 23 and the impaction body 21, and thenveer; meanwhile, the larger microparticles impinge on the impactionplate 23 due to inertia to be collected by the impaction substrate 25and the silicon oil 251 thereon. In this embodiment, the cutoff diameterof the multi-microorifice impactor 20 is 100 nm.

At last, the airflow enters the third chamber 31 through the guidepassage 32, such that the microparticles with diameters smaller than 100nm will be collected by the filter 34 and the clean airflow continue toexit the filter cassette 30 through the outlet 33.

After a predetermined time, stop the sampling and take out the impactionsubstrate 25 along with the aluminum foil 26 and the silicon oil 251 toweigh them, and then calculate the total weight of the RPMs withdiameters of 4 μm to 100 nm; next, take out the filter 34 to weigh itand then calculate the total weight of the NPs with diameters smallerthan 100 nm. In this way, exposure of workers to RPMs and NPs at thesampling place can be accessed.

In light of the special design of the aforesaid embodiment, the NPsampler of the present invention is not only structurally compact andportable but the tangential flow cyclone, the multi-microorificeimpactor, and the filter cassette have highly precise cutoff diameters,respectively.

In particular, the evident difference between the tangential flowcyclone of the present invention and the conventional tangential flowcyclone lies in direction of output airflow. To effectively separate themicroparticles from the airflow, the airflow in each of the conventionaltangential flow cyclones disclosed on the textbooks or in practice isupward in direction as disclosed, for example, in aforesaid U.S. Pat.Laid-open No. 2009/0272202. For a long time, the upward output airflowof the tangential flow cyclone has become a technical prejudice in theart and is contrary to the input airflow required by themulti-microorifice impactor that should be downward in direction. Owingto such characteristic of congenital incompatibilty, none of anynanoparticle sampler composed of the tangential flow cyclone and themulti-microorifice impactor had been available. However, the inventorsof the present invention become aware that if the direction of outputairflow of the tangential flow cyclone is properly changed, it will notonly reach the effect of separating the microparticles but be combinedwith the multi-microorifice impactor to become a low-pressure-droptwo-stage microparticle separator, which is very applicable to theportable nanoparticle samplers stressing on portability. In this way,the precise and convenient microparticle sampling operation can befulfilled.

What are disclosed above is the preferred embodiment of the presentinvention only and the person skilled in the art can simply interchangeor modify the structure, e.g. modifying the cutoff diameter of eachcomponent or respective components are connected by other means;modifying the U-shaped flow guide hole of the fastening plate to othershape; or further dividing it into a plurality of guide holes forcommunication with the upper and lower chamber.

Although the present invention has been described with respect to aspecific preferred embodiment thereof, it is in no way limited to thespecifics of the illustrated structures but changes and modificationsmay be made within the scope of the appended claims.

What is claimed is:
 1. A portable nanoparticle sampler comprising: atangential flow cyclone having a cyclone body and an outflow duct, thecyclone body having an annular portion, a top plate, and a bottom plate,the top plate being mounted to a top side of the annular portion, thebottom plate being mounted to a bottom side of the annular portion, afirst chamber being defined between the annular portion, the top plate,and the bottom plate, an inlet being formed on the annular portion forcommunication with the first chamber, the outflow duct running throughthe bottom plate and having an entrance and an exit, the entrance beinglocated inside the first chamber and higher than the inlet in elevation,the outflow duct being adapted to enable the airflow entering the firstchamber to downwardly exit the tangential flow cyclone through theentrance and the exit by order; a multi-microorifice impactor locatedbelow the tangential flow cyclone and having an impaction body, a nozzlebase, and an impaction plate, the impaction body defining a secondchamber therein, the nozzle base having a plurality of nozzlescommunicating with the exit and the second chamber, the impaction platebeing located inside the second chamber and right below the nozzle base;and a filter cassette located below the multi-microorifice impactordefining a third chamber therein and having a guide passage, an outlet,and a filter, the filter being mounted inside the third chamber andpartitioning the third chamber into a filtration chamber and an outtakechamber, the guide passage communicating with the second chamber and thefiltration chamber, the outlet communicating with the outtake chamber.2. The portable nanoparticle sampler as defined in claim 1, wherein thebottom plate of the cyclone body is detachably mounted to a bottom endof the annular portion.
 3. The portable nanoparticle sampler as definedin claim 1, wherein the multi-microorifice impactor further comprises afastening plate and a motor, both of which are located inside the secondchamber, the fastening plate partitioning the second chamber into anupper chamber and a lower chamber and having an axial hole and at leastone guide hole communicating with the upper and lower chambers, themotor having a rotary shaft inserted into the axial hole andsynchronically rotatably connected with the impaction plate; theimpaction plate and the motor are located inside the upper and lowerchambers, respectively.
 4. The portable nanoparticle sampler as definedin claim 1, wherein the second chamber comprises a taper-shaped bottomside.
 5. The portable nanoparticle sampler as defined in claim 1,wherein the multi-microorifice impactor further comprises an impactionsubstrate disposed on a top side of the impaction plate, the impactionsubstrate being coated with silicon oil.
 6. The portable nanoparticlesampler as defined in claim 5, wherein the impaction substrate is aTeflon filter.
 7. The portable nanoparticle sampler as defined in claim6, wherein the multi-microorifice impactor further comprises an aluminumfoil mounted between the impaction substrate and the impaction plate. 8.The portable nanoparticle sampler as defined in claim 5, wherein themulti-microorifice impactor further comprises an aluminum foil mountedbetween the impaction substrate and the impaction plate.
 9. The portablenanoparticle sampler as defined in claim 1, wherein each of the nozzlesis defined by a smooth annular wall to have an upper opening and a loweropening, the lower opening being smaller than the upper opening indiameter.